In some conventional semiconductor integrated circuits (ICs), an ID showing a production history, manufacturer's number, or the like of an IC chip is stored in an ID reference register provided in the IC chip. The ID is read by an external CPU and used for various purposes.
FIG. 13 shows an example of a connection between such a conventional semiconductor IC and an external circuit. In FIG. 13, an internal circuit 100 of a semiconductor integrated circuit has an ID generation circuit 101 which generates an ID, an ID reference register 102 for storing the ID, and a built-in memory 103. The built-in memory 103 is connected to an external CPU 200 through a terminal 104 and is used as a cache memory or the like for the CPU 200. The ID showing a production history, manufacturer's number, or the like of the IC chip is generated in the ID generation circuit 101 and stored in the ID reference register 102. The ID is read by the external CPU 200 through the terminal 105. Firmware 201, which is one type of software, recognizes the ID and specifies the production history, manufacturer's number, and the like of the IC chip, thereby appropriately controlling each IC.
However, about one hundred are required in the case of an 8-bit address to provide the ID reference register 102, thereby increasing the circuit scale.
The circuit scale may be decreased by storing the ID in a work area (area for storing general data) of the built-in memory 103 when resetting the IC. This may cause a problem in which general data may be overwritten in the same address of the memory in which the ID has been written, thereby making it impossible to refer to the ID.
It is possible to prevent the ID from being overwritten by general data by providing a write-only area for the ID outside the work area. However, this decreases the work area.
Accordingly, an object of the present invention is to provide a semiconductor integrated circuit capable of referring to the ID while reducing the circuit scale in the IC required for storing the ID without decreasing the work area of the memory.